شرایط محیطی لازم در زمان بستری نوزادان پره ترم

1. به نام خداوند بخشنده مهربان شرایط محیطی لازم در زمان بستری نوزادان پره ترم

2. The Thermal Environment of theIntensive CareNursery Protecting infants against excessive heat loss: 1- improves theirchances for survival 2-reduces their need to perform heatproducingmetabolicwork 3- eliminates the problemsassociated with rewarming of coldinfants. During intrauterine life, fetal temperature that is about 0.5°C higher thanthe maternal temperature. After birth, the newborn infant is exposed to air and surfaces facing the infant, which have a much lower temperature than that previously experienced in utero. The skin at birth is covered with amniotic fluid,causing heat loss through evaporation in an environment. As a result, the body temperature of the infant decreases. This gives rise to thermogenicresponses that increase basal heat production,andthe skin circulation may decrease to lower the heat losses.

3. شرایط محیطی لازم در زمان بستری نوزادان پره ترم Heat balance in newborn infants depends on the heattransfer between the infant and the environment.* This transfer is related to:1- the temperature،humidity،flow velocity ofenvironment air, thetemperature of the surfaces facing the infant, and surfaces in contact with the infant . After birth, the immediate interventions required toavoid body cooling are to wipe off the amniotic fluid fromthe skin surface to lower the loss of heat through evaporation,andto cover the infant with a warm, dry towel orblanket, or both, to lessen the exposure of the infant's skinto the environment. The extremely preterminfantsusually need other measures to maintain their body temperature,usuallyplacement in an incubator or under a radiantheater* and, if necessary, mechanical ventilation with warmand humidified gas.

4. ROUTES OF HEAT EXCHANGE Heat exchange between the infant and its environment occurs through the skin and through the respiratory tract. Ithas previously been difficult to estimate the heat exchange between the infant and the environment. The introduction of new techniques to measure the evaporation rate from the skin' and from the respiratory tract has permitted the heat loss through evaporation to be determined. It is also possible to calculate the heat loss through other modes of heat exchange, such as radiation, convection, and conduction;

5. RESPIRATORY LOSS OF HEAT Respiratory water and heat exchange take place by thecombined processes of evaporation and convection. Consequently the losses are related to air temperatureand humidityand directly proportional to the rate ofbreathing. In fact,therelatively higher respiratory waterloss observed in preterm infants depends solely on theirhigher rate of breathing. Provision of a warm and humid environment (e.g.,humidifiedincubator) and/or assisted ventilation withuse of adequately warmed and humidified gas will reduce respiratory loss of water andheat to a minimum and aid temperature stability.

7. NEONATAL THERMOREGULATION The exposure to cold, clamping of the umbilical cord, and the general “stress of being born” induce a thermalresponse. This response is part of a homeostatic system with input (detectors) and output (effectors) that is aimed at preserving body temperature. Exposure to cold induces a sympathetic surge that acts on receptors inbrown fat stores (mainly located in interscapular, paraspinal,andperirenal areas) stimulating lipolysis. Thepresence of the protein thermogenin in brown fat uncouplesβ-oxidation, resulting in metabolic production of heat instead of adenosine triphosphate. The metabolicrate of a newborn has been observed to increase up tothreefold when maximally stimulated by cold.However, in the preterm infant fat stores arescarce andnutritional provision often suboptimal, limiting theirthermogeniccapacity.

8. THERMONEUTRALITY thermoneutral zone” is defined as therange of temperature within which the infant can maintaina normal body temperature at minimal metabolicrate with useofnonevaporativeprocesses(vasoconstriction,vasodilation,and/or changes in posture) only. Outside thisrange, body temperature might still be maintained at thecost of an increased metabolism, but if the temperaturedeviates further, inevitable cooling (or warming) will takeplace.

9. NEONATAL THERMOREGULATION Even a slight longtermexposure to cold will increase thermogenesis,consumeoxygen and substrate stores, and impact negatively on growth.

10. WHAT TEMPERATURE SHOULDBE AIMED FOR? Normal human central body temperature is considered to be 37.0- +05― However, it is evident that seemingly well babies with central temperature keptwithin this range may suffer from cold stress (i.e., display increased metabolic rate owing to thermogenesis). In the preterm infant, to minimize the risk of cold stress when caring for infants with limitedthermoregulatory capacity, it has been shown to be adequate to aim for higher core temperatures within the range of37.6 to 38.2° C, or the slightly wider range of 37.5 to 38.5° C. Such core temperatures in an infant without signs of overwarming (vasodilation, signs of discomfort, or inversion of the central-peripheral temperature difference) may be considered normal

11. CONVECTIVE THERMALSUPPORT—INCUBATOR CARE In a modern double-walled, convectively heated incubator, the warm air is directed so that the walls of the incubator are also kept warm. With a low airflow velocity (<0.1 m/s), the convective heat transfer will depend on the gradient between the skin and the airtemperature, and the vapor pressure gradient close to the skin will be maintained, avoiding an increased evaporative heat loss. Adding the feature of double wall design also reduces the radiant heat loss to the inner walls of the incubator. In a single wall incubator, the “working” temperature in the incubator will be lower than the set air temperature because of the higher radiant loss of heat. Moreover, it will be influenced by room temperature. As a general rule, the air temperature in a single wall incubator has to be increased 1° for every 7° C difference between room and incubator air temperature, as compared with the double wall incubator.

12. CONVECTIVE THERMALSUPPORT—INCUBATOR CARE The incubator is controlled thermostatically by air or infant temperature. Both modes are capable of providinga stable thermoneutral environment Infant skin temperature servo control has the advantage of providing a more stable body temperature underchanging care conditions, different ventilation modes,opening of port holes, and so on. However, there is a risk that the probe may become detached, which may lead tooverwarming, although usually this is not severe. Whenusing skin servo-controlled incubator temperature, theuse of body temperature as a possible signal of disease(hypovolemia, sepsis) has to be replaced by monitoringincubator temperature, which might not be as intuitive. An anterior abdominal skin temperature of 36.5° C hasbeen widely used for servo control of incubator air temperature, but may be too low to ensure thermoneutrality. An abdominal skin (or back to mattress) temperaturesetting of 37.0° C may be preferable.

13. CONVECTIVE THERMALSUPPORT—INCUBATOR CARE Air temperature servo control usually provides a more stable environment, but makes it necessary to frequently determine infant temperature, thus adding further to the load of procedures disturbing the infants. For both modes, Although reserving high ambient humidification (70%-90%) for the first postnatal week of the extremely preterm (<28 weeks) infant, a medium level of 40% to 50% can be recommended for general incubator care

14. RADIANT THERMAL SUPPORT—RADIANT WARMERS Radiant warmers provide excellent accessibility and visibility for the care of the newborn infant and have, therefore,become widely used in neonatal intensive care The high power output of the device explains the effectivenessand speed with which a hypothermic infant can be warmed. On the other hand, harmful overheating can rapidly occur unless careful monitoring (preferably continuous)of infant temperature is instituted. Because ambient humidity is low and air velocity at times relatively, heat loss through evaporation and convectionmay be extensive but can be compensated for by radiantheat gain. An anterior abdominal temperature of 37.0°C is generallyrecommended for servo control of radiant heat output at least as a starting point.

15. RADIANT THERMAL SUPPORT—RADIANT WARMERS A transparent heat shield positioned over the infant may influence the heat exchange (occurring through convection, evaporation, and radiation) and result in reduced losses of heat. However, such a shield interpositioned between the infant and radiant heat source will also disrupt the servo-control mechanism and reduce direct radiant heat delivery to the infant, which may intervene with thermal control.

17. The Sensory Environment of theIntensive Care Nursery Sensory development begins early in fetal life in an environment that is quite different from that of the neonatal intensive care unit (NICU). In an uncomplicated pregnancy,the fetus spends the full gestational period in a warm, dark, contained womb that is the source of extensive kinesthetic, auditory, and gustatory stimuli. The NICU unavoidably and dramatically alters this normal progression of sensory development Not only are familiar stimuli replaced by unfamiliar ones, but they also are apprehended by the infant in a much different fashion—auditory stimuli arrive through an air medium rather than the liquid and solid medium of the amniotic fluid and uterus, tactile stimuli are frequently uncomfortable or painful, visual stimuli may have little relationship with a circadian rhythm,.

18. Overview In the last 3 months of gestation, the fetal brain increases in mass by 400%, and to an even greater extent in complexity and organization.This is comparable to the400% growth that occurs from term delivery to adulthood,yet we have generally assumed that nearly all learning occurs after birth. In reality, a substantial amount of learning occurs during the third trimester, whether a Baby is in or ex utero.

19. Touch and Movement Touch is the first sense to develop in the fetus, with reflexive movement to a stimulus seen as early as 8 weeks. Movements tend to be gentle, often prolonged(as when the mother is walking), and occur with a definite circadian rhythm. In the NICU, however, an infant may spend an extended period of time lying on a flat mattress, interrupted at irregular and unpredictable intervals to be moved suddenly, unnaturally, and sometimes painfully. The NICU infant is constantly “touched” by monitoring devices, indwelling devices, and surfaces that have a much different consistency and impact on the skin than would be experienced in utero. Skin injury is very common in the most premature infants, which may have an additional effect on the sensory experience in the NICU.

20. Taste and Smell The senses of taste and smell become functional by 24 to 28 weeks’ postconceptional age and soon after reach a level of competence comparable to that of the term infant. Maternal dietary flavors are transmitted to the amniotic fluid and recognized as both flavors and odorsby the term newborn, especially in breast milk.In the NICU, infants are exposed to a multitude of odors and tastes, mostly unfamiliar and many of them noxious. Sometimes, these odors or tastes are associated with other noxious stimuli, and this interaction may affect the infant’s response.

21. Auditory The fetus responds to sound by the end of the second trimester, and extensive development of the auditory system continues in the third trimester of fetal life. The in utero environment transmits sounds to the fetus through a liquid medium (the amniotic fluid) and, to some extent,through a solid medium as the infant approaches term and remains in more extended contact with the uterus. This environment attenuates sound, especially high frequency auditory impulses. The sounds experienced by the fetus are primarily those of the mother—both of voice and bodily functions, and it is clear that by term birth, an infant is able to distinguish its mother’s voice from those of other women, but not that of its father. In the NICU, a cacophony of sounds arrives at the infant’s ear at all hours, transmitted through an air medium that does not attenuate any frequencies.

22. Noise The NICU is filled with technologically advanced machines, health care professionals, and caregivers, all of which directly or in directly generate noise pollution. “Studies have demonstrated that there is a direct link between noise and health. Problems that are related to noise and health include: stress related illness, high blood pressure, speech interference, hearing loss, and sleep deprivation” . Sudden and loud noise leads to physiological and behavioral disturbances including sleep disturbance,, startles, crying, hypoxemia, tachycardia, and inceased intracranial pressure . Increased intracranial pressure can further contribute to intra-ventricular hemorrhage . The Physical Environment

23. Talking should be at a considerately low level and laughing should be discouraged. Equipment should not be placed on incubators and opening and closing ofportholes in the incubator should be done in a gentle manner. Monitoring equipment should be minimal and manufacturers should be encouraged to reduce the noise levels in their products. During the night a noise policy or “quiet period” should be applied. Audible alarms should be replaced by visual alarms, and all units should be transported gently and with care.

24. Light Sources of light in the NICU have increased over the years. Little is known about the effects of light exposure on small infants, but damage to the structure and function of the retina has been documented in animal studies. Light may be reduced by covering isolettes with a blanket. Eyes should always be covered when using phototherapy lights. During quiet time” at night, lights need to be dimmed along with noise reduction rules

25. Handling In extremely small premature infants, their skin is very fragile requiring gentle care. Studies have indicated that for premature infants less than30 weeks gestational age, touch may be more stressful rather than soothing. However, for older premature infants, touching may be helpful. Infants respond differently to different kinds of touch. How often a premature infant is touched should be dependent on how he or she responds. It is recommended that application of bland, sterile oil be applied to small preterm infants to help soothe them. Positioning and handling strategies include enhancing flexion in the arms and trunk and preventing flailing and extensions. By taking these factors into consideration, infant stress may be reduced significantly. Nesting using blankets or commercial positioning devices provides boundaries and reduces infant stress. Kangaroo Mother Care (KMC) is also recommended as a positioning and handling technique for medically fragile infants .

26. The physical and psychological neonatal Intensive care unit (NICU) environment may be the single most important factor in neonatal development. Frequent procedures, handling, and exposure to light and noise may cause physiological stress on infants that increase their length of stay in the NICU and ultimately decrease cognitive development.

27. با تشکر